docs: def as_unit(self, unit, location='suffix', *args, **kwargs):
          """Format subset as with units
  
          :param unit: string to use as unit
          :param location: prefix or suffix
          :param subset: Pandas subset
          """
          f = Formatter(
              as_unit(unit, location=location),
              args,
              kwargs
          )
          return self._add_formatter(f)